With the death toll from two days of demonstrations reaching 26, the BBC reported President Viktor Yanukovych posted a statement on his official website saying the two sides had agreed to "negotiations" while trying to stabilize "the situation in the state in the interests of social peace."
The network said no reason was given for the firing of Col. Gen. Volodymyr Zamana, who was replaced by Adm. Yuriy Ilyin, the leader of Ukraine's navy, in a presidential decree.
The BBC said the agreement to halt the violence came after Yanukovych met with opposition leaders Arseniy Yatsenyuk, Vitali Klitschko and Oleh Tyahnybok. Details of the truce or how it would be put into effect were not disclosed.
"The storming of the Maidan [Independence Square] which the authorities had planned today will not take place," Yatsenyuk said in a statement on the website of his Fatherland party.
"A truce has been declared. The main thing is to protect human life."
Vitali Klitschko's Udar Party said negotiations with the government would resume Thursday.
The Voice of Russia reported a tally by Kiev paramedics and medical facilities showed that in addition to those killed at least 351 people were injured in clashes in the city center.
Also Wednesday, President Barack Obama said the United States holds the Ukrainian government "primarily responsible" for dealing properly with peaceful protesters.
Hours after the White House said the United States would coordinate with the European Union on a response to the violence in Ukraine that has some reports said injured more than 1,000, Obama said in Toluca, Mexico, the United States condemns the violence "in the strongest terms" and is "deeply engaged with our European partners as well as the Ukrainian government and the opposition to try to ensure that that violence ends."
"But we hold the Ukrainian government primarily responsible for making sure that it is dealing with peaceful protesters in an appropriate way, that the Ukrainian people are able to assemble and speak freely about their interests without fear of repression," the president told reporters during an appearance with Mexican President Enrique Pena-Nieto. "And I want to be very clear as we work through these next several days in Ukraine that we're going to be watching closely and we expect the Ukrainian government to show restraint, to not resort to violence in dealing with peaceful protesters."
Obama added, "We've also said we expect peaceful protesters to remain peaceful and we'll be monitoring very closely the situation, recognizing that with our European partners and the international community there will be consequences if people step over the line."
Obama said the Ukrainian military should not "step into what should be a set of issues that can be resolved by civilians."
As Yanukovych and the opposition blamed each other for the violence in Kiev, French President Francois Hollande and Polish Prime Minister Donald Tusk called for "rapid and targeted European sanctions against those leaders responsible for these acts," the Financial Times reported Wednesday.
Other European leaders echoed similar sentiments.
"We have made it clear we would consider taking action against individuals who are responsible for acts of violence within Ukraine," deputy national security adviser Ben Rhodes told reporters aboard Air Force One as Obama traveled to Mexico for the North American Leaders Summit. "We have a toolkit for doing that that includes sanctions."
Rhodes said it would "figure into our calculus" if the Ukrainian government releases prisoners and negotiates with the opposition.
"The leaders of the opposition have disregarded the principle of democracy, which says we obtain power through elections and not on the street," Yanukovych said in an earlier nationally televised address.
Anti-government protesters behind burning barricades threw Molotov cocktails and rocks at raiding police officers in Independence Square Tuesday night.
Protesters torched the headquarters of the ruling Party of Regions and the opposition's headquarters, the Trade Unions House, also was on fire, CNN reported.
At least 10 police officers and a journalist were among the people killed in the violence, the Kyiv Post reported.
Helmeted protesters had hurled rocks, fireworks, broken pieces of paving stones and Molotov cocktails to fight back against riot squads firing stun grenades, water cannons, rubber bullets and, based on medical reports, live ammunition, witnesses said.
The protesters "crossed the limits by calling for people to take up arms," Yanukovych said.
"It is a flagrant violation of the law and those who are responsible will face justice."
Klitschko urged protesters to protect their Independence Square encampment from police, calling it "an island of freedom and we will defend it."
Acting Prime Minister Serhiy Arbuzov said the protesters "are bringing shame" on the country.
The journalist, who died Wednesday, was shot Tuesday night after a group of masked people stopped a taxi in which he was a passenger, a statement by his newspaper, Ukrainian Vesti, said. The group threw Molotov cocktails and beat other passengers in the taxi, the newspaper reported.
The Kyiv Post reported the Security Service of Ukraine indicated a criminal case has been launched into an attempted coup by several politicians.
The violence followed what seemed like a breakthrough in the months-long anti-government protests, after Yanukovych changed his mind about signing political and trade agreements with the European Union in favor of agreements with Russia in November.
The government said it would drop charges against people arrested during the political unrest. Lawmakers had said they would consider amending the constitution concerning presidential powers.
Protesters pulled back from holding Kiev's City Hall for three months but when the speaker of Parliament refused to allow amendments that would limit the president's powers angry people filled the streets, CNN reported.
The government's prosecutor general accused the opposition of breaking "the truce," opening the door for the police crackdown.
Police said the unrest had spread to western Ukraine, with reports of clashes and attacks on government offices in a number of areas, CNN said.
Ukrainian ally Russia said Washington was meddling in Ukrainian affairs by trying to tell "the authorities of a sovereign state what they should do next and how they should do it," an article in Russia's state-run RIA Novosti said.
The U.N. Office of the High Commissioner for Human rights issued a statement Wednesday noting that "preventing further instability and bloodshed is a paramount priority."
The violence came after Moscow announced it was restoring a financial lifeline to Yanukovych's government by buying $2 billion in Ukrainian government bonds.
Yanukovych earlier had pledged not to use force to disperse the protesters.